The present invention relates to strobe lights, such as ignition timing lights, of the type which are powered by a capacitive discharge, and relates particularly to a capacitor charging circuit.
Strobe lights typically comprise a glass lamp in which a gas is sealed. The lamp typically includes two power electrodes and may include a trigger electrode. Energy for activating the lamp or ionizing the gas stored within the lamp is generally stored in one or more capacitors connected in parallel with the lamp. Once a sufficient amount of energy has been stored in the capacitors and it is desired to flash the lamp, a firing pulse is applied to the trigger electrode. The firing pulse ionizes the gas sufficiently to allow current to flow between the two power electrodes, which results in a brilliant flash of the strobe light.
In one known type of strobe light circuit the capacitor is charged by current pulses applied through a transformer and a rectifier. In one such device, disclosed in U.S. Pat. No. 4,095,170, the primary winding of the transformer forms part of the oscillator, which is connected in a push-pull configuration. This arrangement is characterized by relatively high power consumption. In another device, disclosed in U.S. Pat. No. 4,422,016, an electronic switch is connected in the transformer primary circuit, the switch being controlled by a pulse width modulated signal which is derived from the transformer primary current. But the electronic switch is a bipolar transistor which is subject to thermal runaway, with resultant transformer blowout.